KR101030889B1 - Optical deflector and optical instrument using the same - Google Patents

Abstract

The optical deflector of the present invention is configured to support the first and second movable elements for a torsional vibration about the oscillation axis with a support member, a first movable element having an optical deflection element, at least one second movable element, and a vibration axis. At least one first torsion spring, at least one second torsion spring configured to support the second movable element and the support member for torsional vibration about an oscillation axis, and at least one of the first and second movable element And a drive system configured to apply a driving force, the moment of inertia of the second movable element about the oscillation axis being greater than the moment of inertia of the first movable element about the oscillation axis, the direction of the second movable element being perpendicular to the oscillation axis. The length is equal to or less than the length of the first movable element in the direction perpendicular to the vibration axis.

Optical deflector, movable element, torsional vibration, moment of inertia, vibration axis

Description

Optical deflector and optical device using same {OPTICAL DEFLECTOR AND OPTICAL INSTRUMENT USING THE SAME}

1A is a plan view of an optical deflector according to an embodiment of the present invention and a first example of the present invention.

FIG. 1B is a cross sectional view of the optical deflector of FIG. 1A taken along line A-B in FIG. 1A; FIG.

Fig. 2 is a graph for explaining the displacement angle of the scan deflected light by the optical deflector according to the first embodiment of the present invention.

Fig. 3 is a graph for explaining the angular velocity of the scan deflected light by the optical deflector according to the first embodiment of the present invention.

4A is a plan view of an optical deflector according to a second embodiment of the present invention.

4B is a cross sectional view of the optical deflector of FIG. 4A taken along line A-B in FIG. 4A;

5A is a plan view of an optical deflector according to a third embodiment of the present invention.

FIG. 5B is a sectional view of the optical deflector of FIG. 5A taken along line A-B in FIG. 5A.

6A is a plan view of an optical deflector according to a fourth embodiment of the present invention.

FIG. 6B is a cross sectional view of the optical deflector of FIG. 6A taken along line A-B in FIG. 6A;

7 is a perspective view for explaining an optical apparatus according to a fifth embodiment of the present invention.

8 is a plan view for explaining the actuator of the prior art.

9 is a plan view for explaining the vibration device of the prior art.

<Explanation of symbols for the main parts of the drawings>

101: support member

102: first movable element

103: main body

104: vibration axis

105, 106: torsion spring

107: reflective surface

108: magnet

109: mass adjusting member

120: second movable element

112: spacer

111: fixed substrate

The present invention relates to optical deflectors and optical instruments that utilize such optical deflectors such as, for example, image forming apparatuses or display apparatuses. The optical deflector of the present invention can be suitably used for a projection display in which an image is projected based on a deflection scanning of light or an image forming apparatus having an electrophotographic process such as, for example, a laser beam printer or a digital copier.

As such an optical deflector, various types of optical scanning systems or optical scanning devices have been proposed in which a movable element having a reflective surface is sine oscillated to deflect light. An optical scanning system using an optical deflector that performs sinusoidal vibration based on a resonance phenomenon has the following advantages over a scanning optical system using a rotating polygon mirror (polygon mirror). That is, the optical deflector can be miniaturized very low and power consumption is low. In particular, the optical deflector manufactured by Si single crystal and produced through a semiconductor process has excellent durability without theoretically suffering from metal fatigue.

An example of the optical deflector using the resonance phenomenon is the actuator shown in FIG. 8 (see Patent Document 1).

In FIG. 8, the actuator, generally designated 100, comprises a first mass member 1, a second mass member 2 and a pair of support members 3. These components are made of silicon, for example. The light reflecting element 21 is provided on the surface of the second mass member 2 of the actuator. As shown in FIG. 8, the actuator 100 couples the first mass member 1 and the support member 3 and a pair of firsts for the covering operation of the first mass member to the support member 3. It has an elastic coupling member 4. In addition, the actuator couples the first mass member 1 and the second mass member 2 and a pair of second elastic couplings for the covering operation of the second mass member 2 with respect to the first mass member 1. It has a member 5. 6 indicates an opposing substrate.

As described above, the two degree of freedom vibration actuator includes two resonance frequencies (intrinsic vibration mode) in which the amplitudes of the first and second mass members 1 and 2 are large and the amplitude of the first mass member 1 is almost zero. It has one anti-resonant frequency (unique vibration mode). In the actuator having the above-described structure, by using the lower one of the two frequencies for driving, the displacement angle (rotation angle) of the second mass member 2 can be increased while keeping the amplitude of the first mass member 1 small.

Some optical deflectors using the resonance phenomenon use a method of simultaneously exciting two or more natural vibration modes in the torsional vibration direction to perform sinusoidal light scanning and other light scanning (Patent Document 2).

9 is a plan view of such an optical deflector. As shown in Fig. 9, the flat plate movable element 1001 is supported by two torsion springs 1011a and 1011b at its upper and lower portions. The frame-shaped movable element 1002 supports these torsion springs 1011a and 1011b inward, while the top and bottom portions thereof are supported by two torsion springs 1012a and 1012b, as shown in FIG. . The frame-shaped support frame 1021 supports the torsion springs 1012a and 1012b from the inside. The movable elements 1001 and 1002 and the torsion springs 1011 and 1012 have two natural vibration modes with a frequency ratio of 1: 2. The optical deflector is driven by sawtooth vibration by simultaneously exciting these two vibration modes, and an optical scan with a small angular velocity change is provided. 1000 indicates a plate member and 1041 indicates a permanent magnet.

[Patent Documents]

1: Japanese Patent Application Publication No. 2005-099760 and corresponds to US Patent Application No. 2005/088715 (A1)

2: Japanese Patent Application Publication No. 2005-208578 and corresponds to US Patent Application No. 2006/152785 (A1)

In an electrophotographic process such as a laser beam printer, a photosensitive member is scanned by a laser beam to form an image thereon. When an optical deflector having a plurality of movable elements and a plurality of torsion springs is used to perform light scanning with a large displacement angle, it is preferable that the plurality of natural vibration modes are arranged in a desired relationship and the displacement angle is stable. However, in the optical deflector having a plurality of movable elements and a plurality of torsion springs, it is not easy to set a plurality of natural vibration modes in a desired relationship due to dispersion of processing accuracy. In addition, when the displacement angle of the optical deflector is large, it is not easy to maintain the displacement angle stably due to air resistance or the like.

According to one aspect of the present invention, an optical deflector comprises: a first movable element having a support member, an optical deflecting element, at least one second movable element, and a first oscillation element for torsional vibration about an oscillation axis; At least one first torsion spring configured to support a second movable element, at least one second torsion spring configured to support the second movable element and the support member for torsional vibration about an oscillation axis; And a drive system configured to apply a driving force to at least one of the first and second movable elements, wherein the moment of inertia of the second movable element relative to (ie, around) the oscillation axis is dependent on the first axis relative to the oscillation axis. It is larger than the moment of inertia of the movable element, and the length of the second movable element in the direction perpendicular to the vibration axis is less than or equal to the length of the first movable element in the direction perpendicular to the vibration axis.

According to another aspect of the present invention, an optical apparatus includes a light source, the light deflector described above, and a photosensitive member and an image display member, wherein the light deflector deflects light from the light source and at least a portion of the deflected light. It is configured to advance to the photosensitive member or the image display member.

According to the present invention, the length of the second movable element in the direction perpendicular to the moment of inertia or oscillation axis of the second movable element is set as described above. This structure achieves an optical deflector in which a plurality of natural vibration modes of the optical deflector are easily adjusted in a desired relationship, and furthermore, the displacement angle is stably maintained even when the displacement angle is relatively large. In the optical apparatus using such an optical deflector, a large but stable displacement angle is achieved by the present invention.

These and other objects, features and advantages of the present invention will become more apparent upon consideration of the following description of the preferred embodiments of the present invention in conjunction with the accompanying drawings.

Hereinafter, exemplary embodiments of the present invention will be described with reference to the accompanying drawings.

1A and 1B, an embodiment of an optical deflector according to the present invention will be described. FIG. 1A is a plan view of the optical deflector according to the present embodiment, and FIG. 1B is a sectional view taken along the line A-B of FIG. 1A. The optical deflector of the present embodiment includes a support member 101, a first movable element 102 having a reflective surface 107, which may be an optical deflection element, a second movable element 120, and a vibration shaft 104. It may include a torsion spring (105, 106) for elastically supporting the support member 101, the first movable element 102 and the second movable element 120 to the center. The second movable element 120 includes a main body 103, a mass adjusting member 109 such as metal disposed on the upper surface of the main body for adjusting the mass, and a magnet (hard magnetic body) 108 provided at the bottom of the main body. ) May be included. The first movable element 102 may be elastically supported by the second movable element 120 via the first torsion spring 105 for torsional vibration about the oscillation shaft 104. The second movable element 120 may be elastically supported by the support member 101 via the second torsion spring 106 for torsional vibration about the vibration shaft 104. The support member 101 may be fixed to the fixed substrate 111 via the spacer 112.

The optical deflector of the present embodiment may further include a driving unit for driving the first and second movable elements 102 and 120 and a driving control unit for controlling the driving unit. Typically, the drive unit may include means for applying a torque to at least one of the first and second movable elements 102 and 120 to resonate drive them. Here, the driving unit may include a coil 110 and a magnet 108 for applying torque to the second movable element 120 to resonate drive the first and second movable elements 102 and 120. The magnet 108 may be disposed on the second movable element 120 and the coil 110 may be mounted on the substrate 110. The driving controller may be, for example, a driving control circuit for supplying a driving current according to a driving signal to the coil 110 of the driving unit. The driving unit may use an electromagnetic method in the present example, or may use, for example, an electrostatic method or a piezoelectric method.

The optical deflector of the present embodiment may have two natural vibration modes having different frequencies. These two natural vibration modes (primary natural vibration mode and secondary natural vibration mode) may be excited simultaneously or separately by the drive control unit and the drive units 108 and 110. By doing so, the first and second movable elements 102 and 120 are torsionally resonantly driven about the oscillation shaft 104 at a relatively large displacement angle with respect to the support member 101. When these two torsional natural vibration modes are simultaneously excited, the optical deflector of this embodiment is driven by vibrations based on superimposed sinusoidal waves.

The optical deflector of this embodiment has a moment of inertia I ₂ of the second movable element 120 with respect to the oscillation axis 104 than an moment of inertia I ₁ of the first movable element 102 with respect to the oscillation axis 104. It can be enlarged. In addition, the length 122 of the second movable element 120 in the direction perpendicular to the vibration axis 104 may be equal to or less than the length 121 of the first movable element 102 in the direction perpendicular to the vibration axis 104. Can be. When the shape of the first or second movable element 102 or 120 is not rectangular (including square), the length in the direction perpendicular to the vibration axis 104 is perpendicular to the vibration axis 104 and at the vibration axis 104. It may refer to the length to the furthest point.

Hereinafter, the functions and operations of the present embodiment will be described. In the optical deflector according to the present embodiment, the moment of inertia I ₂ of the second movable element 120 (when connected to the support member 101) with respect to the vibration axis 104 is relative to the vibration axis 104. It may be larger than the moment of inertia I ₁ of the first movable element 102 (when connected to the second movable element 120). This structure allows the natural vibration modes of vibration to be easily adjusted so that these natural vibration modes can be placed in a desired relationship.

For example, when the moments of inertia of the first and second movable elements 102 and 120 have a relationship of I ₁ > I ₂ , the change of the moment of inertia I ₁ greatly changes both natural vibration modes. In addition, a change in the moment of inertia I ₂ likewise results in a significant change in both natural vibration modes. Therefore, it is very difficult to adjust two torsional natural vibration modes separately.

On the other hand, when the moments of inertia of the first and second movable elements 102 and 120 have a relationship of I ₁ <I ₂ , one of the primary natural vibration mode and the secondary natural vibration mode of the optical deflector is mainly the inertia moment. Can be changed by changing (I ₁ or I ₂ ). Preferably, I ₂ should be at least four times I ₁ .

Thus, even though the two torsional natural vibration modes do not satisfy the desired relationship due to the dispersion of the shape caused in the manufacture of the optical deflector, these two torsional natural vibration modes are for example at least _{one of the} moments of inertia I ₁ , I ₂ . By adjusting one can be adjusted to the desired frequency relationship.

Even if the frequencies f ₁ and f ₂ of the natural vibration mode are deflected at the target frequency due to error factors such as process tolerances of the vibration system including the first and second movable elements, these frequencies f ₁ , f ₂ ) May be appropriately adjusted based on the relationship of the moment of inertia described above. It will be described in detail below.

In the optical deflector of the present embodiment that satisfies the above-described inertia moment, the frequencies f ₁ and f ₂ of the first and second natural vibration modes centering on the vibration axis 104 are expressed by Equation 1 below. Given the approximate relationship, in this equation I ₁ is the moment of inertia of the first movable element 102 and I ₂ is the moment of inertia of the second movable element 120 and k ₁ and k ₂ are each paired first and Is the spring constant of the second torsion springs 105, 106. Also, with respect to the right side abbreviation, the negative sign is chosen in case of f ₁ and the positive sign is chosen in case of f ₂ .

[Equation 1]

In Equation 1, when the difference between I ₁ and I ₂ is not large, both frequencies f ₁ and f ₂ change according to the increase and decrease of I ₁ and I ₂ . Therefore, in order to adjust the frequencies f ₁ and f ₂ to the desired frequencies, respectively, the increase and decrease of I ₁ and I ₂ must be enlarged or it is impossible to adjust the frequency to the desired value.

Meanwhile, in Equation 1, I ₁ << I ₂ changes in the frequency (f _1, f ₂₎ is obtained by controlling a case, the moment of inertia of the two movable elements (I _1, I ₂₎ (e. G., I ₂ is more than 4 times that of I ₁₎ is the frequency ( f ₁ ) changes with increasing or decreasing I ₁ and frequency (f ₂ ) changes with increasing or decreasing I ₂ , while increasing or decreasing I ₁ hardly changes frequency (f ₂ ) and increasing or decreasing I ₂ is frequency (f ₁ ) Has almost no change.

When Equation 1 is applied to the vibration system having two second movable elements 220a and 220b as shown in Fig. 4, the sum of the moments of inertia of these two second movable elements 220a and 220b is zero. 2 may be used as the moment of inertia (I ₂ ) for the movable element. Also, with respect to the spring constant K _{1 of} the first torsion spring, the sum of the spring constants of the first torsion springs 205a and 205b can be used. Similarly, with respect to the spring constant K _{2 of} the second torsional spring, the sum of the spring constants of the second torsional springs 206a and 206b can be used.

The vibration system of the present embodiment is arranged such that the permanent magnet 108 and the mass adjusting member 109 are provided only in the second movable element 120 in consideration of the characteristics of the vibration system as described above, thereby ensuring improved scanning reproducibility. While I ₁ << I ₂ can be satisfied. In particular, setting the magnet 108 only to the second movable element 120 allows the magnet's mass to be used as an inertia moment to ensure an I ₁ << I ₂ relationship while using the magnet as a torque generation source.

In the vibration system of the present embodiment, at least one of the first movable element 102 and the mass adjusting member 109 is partially removed to reduce the appropriate amount of I ₁ and I ₂ , thereby causing the frequencies f ₁ and f ₂ to be reduced. Is adjusted to satisfy the desired relationship (ie, the relationship defined by Equation 2 or Equation 4 described later). Thus, even if the frequency of the natural vibration mode is deflected at a desired value, it can be appropriately matched. That is, in this case, by deflecting the driving frequency and measuring the amplitude of the vibration system, any deflection of the frequencies f ₁ and f ₂ of the natural vibration mode deviating from the target value can also be determined. The necessary adjustment amount σI ₁ , σI ₂ may be calculated according to Equation 1 based on the measured values. Thereafter, the frequencies f ₁ and f ₂ can be precisely adjusted as desired by partially removing at least one of the first movable element 103 and the mass adjusting member 109 using a laser beam, for example.

In particular, the magnet 108 and the mass adjusting member 109 share the function of providing the moment of inertia to the second movable element 120 with respect to the adjustment amount σI ₂ , so that the volume per volume to be removed by laser beam processing is shared. The adjustment amount σI ₂ is enlarged as compared with the case where a part of the second movable element 120 itself is removed. Therefore, the frequency control of the natural vibration mode using the laser beam processing can be made at a high speed and cheap manufacturing is ensured. In addition, since the adjustment amount σI ₂ per removal volume is large, the frequency adjustable range can be increased even when the width of the second movable element 120 is small. Due to these features, not only the scanning stability is improved but also the vibration system can be miniaturized. Therefore, when the device is made of a single crystal silicon substrate according to the semiconductor manufacturing method, the manufacturing cost becomes even cheaper.

On the other hand, the length 122 of the second movable element 120 in the direction perpendicular to the vibration axis 104 is made larger than the length 121 of the first movable element 102 in the direction perpendicular to the vibration axis 104. In this case, the air resistance acting on the second movable element 120 becomes large. In consideration of this, preferably, the length of the second movable element 120 in the direction perpendicular to the vibration axis 104 is shorter than the length of the first movable element 102 in the direction perpendicular to the vibration axis 104. Can be. This structure reduces air resistance and improves displacement angle stability. Thus, even if the optical deflector is driven with a large displacement angle, excellent displacement angle stability is ensured.

In addition, by making the moment of inertia of the second movable element 120 large, the amplitude amplification factor (resonance fineness Q value) of the natural vibration mode can be improved. Displacement angle stability is improved by increasing the coronal moment to reduce the dispersion of vibrational energy by increasing the amplitude amplification factor. Thus, even if the optical deflector is driven with a large displacement angle, excellent displacement angle stability is ensured.

In the optical deflector of this embodiment, the length 122 of the second movable element 120 in the direction parallel to the vibration axis 104 is the length of the first movable element 102 in the direction parallel to the vibration axis 104. It can be set as follows. Due to this structure, the air resistance of the second movable element 120 during the torsional vibration is further reduced, and the displacement angle stability is improved.

In addition, in the optical deflector of the present embodiment, the thickness of the second movable element 120 may be larger than that of the first movable element 102. Due to this structure, the moments of inertia of the first and second movable elements 102 and 120 can be easily set to satisfy the I ₁ <I ₂ relationship.

The optical deflector of this embodiment may have a structure in which the support member 101 is connected to one of the plurality of torsion springs. Due to this structure, even if the fixing point of the support member 101 is deformed due to an unexpected force generated by the stress generated when the support member 101 is fixed or any thermal stress, the first and second movable elements are deformed. Stresses hardly act on 102 and 120. Therefore, the fall of the top view (surface precision) of the reflective surface 107 is prevented. In particular, when the second movable element 120 is composed of a single element, since the air resistance is very small, the displacement angle stability is improved and at the same time miniaturization of the optical deflector is achieved.

The optical deflector of the present embodiment may have a structure in which the first and second movable elements 102 and 120 are connected to the support member at both ends of the plurality of torsion springs. By having this structure, due to the support at both ends (each torsion spring is fixed at two points), unnecessary vibrations other than the torsion springs can be more reliably prevented during torsional vibrations. In particular, even when the optical deflector is equipped with a movable element having a large moment of inertia that easily causes unnecessary vibration during torsional vibration, the occurrence of such unnecessary vibration is suitably prevented.

The optical deflector of this embodiment may have a structure in which the first movable element 102 is provided by a single component or a single material. In this structure, since the first movable element 102 on which the reflective surface 107 is formed is made of a single part, deformation of the reflective surface 107 is surely prevented.

The optical deflector of the present embodiment may have a structure in which the second movable element 120 is provided by a plurality of components as described above. In this structure, since the second movable element 120 may include components having a large moment of inertia (eg, the mass adjusting member 109 or the magnet 108), the inertia of the second movable element 120 may be reduced. It may be easy to increase the moment. Therefore, the moments of inertia of the first and second movable elements 102 and 120 can be easily set to satisfy the I ₁ <I ₂ relationship (see the first embodiment described later).

The optical deflector according to the present exemplary embodiment may have a structure in which the above-described plurality of components of the second movable element 120 are disposed with the vibration shaft 104 interposed therebetween. For example, as shown in FIGS. 1A and 1B, components such as metal members are present along a direction perpendicular to the flat surface portion of the second movable element 120 with the vibration axis 104 interposed therebetween. May be placed in position. In this case, the moment of inertia of the second movable element 120 can be made very large. Alternatively, components such as metal members may be disposed along a direction parallel to the flat surface portion of the second movable element and disposed at a position between the vibration shafts 104 therebetween. Also in this case, the moment of inertia of the second movable element 120 can be made very large. Therefore, in this structure, the moment of inertia I ₂ of the second movable element can be easily increased.

The optical deflector of the present embodiment may have a structure in which the center of gravity of the second movable element 120 is aligned with the vibration axis 104. In this structure, unnecessary vibrations other than torsional vibrations during torsional vibrations can be reliably prevented (see the third embodiment described later). In particular, even if the optical deflector has a movable element having a large moment of inertia that easily causes unnecessary vibration during torsional vibration, such unnecessary vibration is properly prevented.

The optical deflector of the present embodiment may have a structure in which at least one of the aforementioned components is made of metal. In this structure, since the second movable element 120 includes a metal having a high specific gravity, the moment of inertia of the second movable element 120 can be easily increased. Therefore, the moments of inertia of the first and second movable elements 102 and 120 can be easily set to satisfy the I ₁ <I ₂ relationship.

The optical deflector of the present embodiment may have a structure in which at least one of the aforementioned components is the hard magnetic material 108 as described above. In this structure, the moment of inertia of the second movable element 120 may be increased on the one hand, and on the other hand, when the driving unit uses electromagnetic force, a large driving force may be generated even with a small current. Therefore, power consumption becomes small.

The optical deflector of this embodiment may have an integral structure in which the first movable element, the second movable element, the torsion spring and the support member are made of single crystal silicon. In such a case, these components can be manufactured in batch processing by a micromachining method using a semiconductor manufacturing process. Thus, the optical deflector can be manufactured with very high processing precision.

The optical deflector of the present embodiment may have at least two natural vibration modes having different frequencies, and the first movable element 102 may be simultaneously torsionally vibrated about the vibration axis 104 according to the at least two natural vibration modes. Can be. In this structure, the optical deflector is driven based on the vibration of the overlapping sinusoidal wave.

The optical deflector of this embodiment may have a structure in which one frequency of two different natural vibration modes is approximately twice or three times the frequency of the other natural vibration modes. In this case, the moment of inertia of the second movable element (I ₂₎ is not to be less than 1.8 times of the moments of inertia (I ₁₎ of the first movable element. As a result, the first movable element can be driven by sawtooth wave (or triangular wave) vibration (see the first embodiment described later).

The optical deflector of this embodiment may have a structure in which at least one of the first and second movable elements intersects the plane at a plurality of positions when defining a plane perpendicular to the vibration axis 104 ( See the third embodiment described later). In this structure, even if the movable element has a relatively small area, the moment of inertia can be increased. In addition, the adjustment of the mass is easy, so that the moment of inertia can be adjusted relatively easily.

An optical apparatus such as a display apparatus or a printer having an optical deflector according to an exemplary embodiment of the present invention may include a light source, the optical deflector, a photosensitive member, and an image display member. The light deflector may deflect light emitted from the light source to advance at least a portion of the light deflected onto the photosensitive member or the image display member.

Hereinafter, the present invention will be described in more detail with reference to specific embodiments.

[First Embodiment]

Hereinafter, a first embodiment of the present invention will be described. This example corresponds to the above-described embodiments. 1A and 1B show the structure of the optical deflector according to the first embodiment. FIG. 1A is a plan view of the optical deflector and FIG. 1B is a sectional view taken along the line A-B of FIG. 1A. The optical deflector includes a support member 101, a first movable element 102 having a reflective surface 107, a second movable element 120, and a support member 101, made of a vibration shaft 104. Torsion springs 105 and 106 for elastically coupling the first movable element 102 and the second movable element 120. The fragrance fragrance may further include a drive unit for applying torque to the second movable element 120 and a drive control unit for controlling the drive unit to generate resonance driving of the first and second movable elements 102 and 120. Can be. The driving unit includes a magnet 108 disposed on the second movable element 120 and a coil 110 mounted on the substrate 110.

The first movable element 102 has a length 121 of 3 mm in the direction perpendicular to the vibration axis 104 and has a size of 1 mm in the direction parallel to the vibration axis. The second movable element 120 has a length 122 of 2.8 mm in the direction perpendicular to the vibration axis 104 and has a size of 1.5 mm in the direction parallel to the vibration axis. The silicon member (main body) 103 and the torsion springs 105 and 106 of the support member 101, the first and second movable elements 102 and 120 are formed of single crystal silicon according to photolithography and dry etching of a semiconductor manufacturing method. The substrate is made of an integral structure. Therefore, an optical deflector with a very high processing precision and a very small size can be manufactured.

The reflective surface 107 of the first movable element 102 is made of aluminum and is formed by vacuum vapor deposition. Of course, the reflective surface can be made of any other material, for example gold or copper. The top surface may be provided with a protective film. The second movable element 120 has a silicon portion 103, a hard magnetic body 108, and a copper member (mass control member) 109.

The driving principle of this embodiment is explained. The hard magnetic body 108 is polarized (magnetized) in a direction perpendicular to the vibration axis 104. The optical deflector of this embodiment has two torsional natural vibration modes having different frequencies f ₁ and f ₂ . As the driving control unit and the driving unit apply AC current to the coil 110, an electromagnetic force is generated and applied to the hard magnetic material 108. Thus, two torsional natural vibration modes are simultaneously excited. As a result, torsional resonance driving of the first and second movable elements 102 and 120 around the oscillation shaft 104 is generated at a relatively large displacement angle with respect to the support member 101.

The driving principle of the sawtooth vibration of the optical deflector according to the present embodiment will be described. About a torsional oscillation around the torsion axis 104, a vibration system of the present embodiment the optical deflector has a frequency (f ₁₎ 1 primary natural vibration mode, and the reference secondary of approximately double the frequency (f ₂₎ of the frequency of the It has a natural vibration mode. Such a vibration system can be treated as a vibration system having "2" degrees of freedom for torsional vibration.

On the other hand, the fixed coil 110 drives the vibration system in accordance with the synthesized drive signal based on the reference frequency (f ₀ ) (target drive frequency determined by the application specification of the system) and the frequency 2f _{0 which} is approximately twice the reference frequency. . The reference frequency f ₀ and the natural vibration mode frequencies f ₁ and f ₂ have a relationship described below, and the optical deflector of the present embodiment performs sinusoidal synthesis driving based on a large dynamic magnification (amplification amplification factor) of the natural vibration mode. Perform with low power consumption.

In particular, the natural mode frequency f ₁ is designed to be close to the reference frequency f ₀ . Here, when the mode attenuation ratios (representing the sharpness of the peaks of the same magnification frequency characteristic curve at the intrinsic mode frequencies and approximately equal to 1 / 2Q) are expressed as γ1 and γ2, respectively, the range is It is expressed as follows.

[Equation 2]

In addition, in the present specification, the dichotometry Δ related to the frequency ratio of the frequencies f ₁ and f ₂ is defined as follows and a range corresponding to " approximately integer product " The illuminance degree Δ is defined as Δ = N (f ₁ / f ₂ ) with the index that the frequencies f ₁ and f ₂ of the vibration system are in the “N times” relationship. For example, in this specification, "about twice" refers to the range represented by Equation 3 below.

&Quot; (3) &quot;

In addition, in this embodiment, the frequency ratio is in the following range.

&Quot; (4) &quot;

In the vibration system of this embodiment, γ ₁ is approximately 0.001 and γ ₂ is approximately 0.00025. In this embodiment, vibrations of f ₀ and 2f ₀ are excited by the fixed coil 110 near the peaks of the two natural vibration modes and the vibration system is driven based thereon. In particular, in the range defined by Equation 2, with respect to the vibration of the frequency f ₀ , which is the main component of power consumption for sinusoidal synthesis driving, the range of large dynamic magnification (amplification amplification factor) of the first natural vibration mode is large. Can be used. Therefore, the power consumption of the optical deflector is lowered.

Hereinafter, the driving method will be described in detail. FIG. 2 illustrates the displacement angle of the first vibrator 102 during the torsional vibration of the frequency f ₀ as a graph with the horizontal axis as the time t (in this specification, by the reciprocating vibration of the movable element and the optical deflector). Since the displacement angles of the deflected scanned light differ only in constants, they are treated equivalently). In particular, Figure 2 shows a first portion corresponding to the first movable element 102, one period of the torsional vibration (T ₀₎ of the _{(-T 0/2 <X <} T 0/2).

Curve 61 shows the component of the reference frequency f ₀ of the drive signal that energizes the fixed coil 110. This is the sinusoidal vibration represented by Equation 5 below, with a reciprocating oscillation in the maximum amplitude range (± φ1), time t, and each frequency w ₀ = 2πf ₀ .

[Equation 5]

Curve 62, on the other hand, represents a frequency component that is twice the reference frequency f ₀ , which is a sinusoidal vibration that vibrates in the maximum amplitude range (± φ ₂ ) and is represented by Equation 6 below.

&Quot; (6) &quot;

Curve 63 represents the displacement angle of the torsional vibration of the first movable element 102 generated as a result of the above-described driving. For torsional vibration about the torsional axis 104, the optical deflector has a natural vibration of the frequency f ₁ which is adjusted near the reference frequency f ₀ and the frequency 2f _{0 which} is twice the reference frequency as described above. It has a second natural vibration mode of mode and frequency f ₂ . Thus, both the resonance excited by the drive signal corresponding to θ ₁ and the resonance excited by the drive signal corresponding to θ ₂ occur in the optical deflector. That is, in the curve 63, the displacement angle of the first movable element 102 depends on the vibration by the superposition of these two sinusoidal vibrations, that is, the sawtooth wave vibration represented by Equation 7 below is generated.

[Equation 7]

FIG. 3 shows curves 61a and 63a and straight line 64a obtained by differentiating curves 61 and 63 and straight line 64 of FIG. 2 and explain the angular velocity of these curves. Compared to the curve 61a showing the angular velocity of the sinusoidal vibration of the reference frequency f ₀ , the curve 63a showing the angular velocity of the sawtooth reciprocating vibration of the first movable element 102 has the maximum angular velocity in the interval N-N ', respectively. It is maintained within a range having an upper limit and a lower limit corresponding to the angular velocity V ₁ at the value and the angular velocity V ₂ at the minimum value. Thus, in applications based on optical deflection scanning using optical deflectors, V ₁ and V ₂ are within the available error range of the angular velocity from the straight line 64a corresponding to the constant angular velocity scanning, and the interval N-N 'is in fact constant angular velocity scanning. Can be considered an area.

As mentioned above, compared to vibrations based on displacement angles along sinusoids, sawtooth reciprocating vibrations provide a much wider range of substantially constant angular velocities relative to the angular velocity of the deflection scan. Thus, the ratio of the available area to the total deflection scan area is significantly expanded. In addition, sawtooth driving ensures regular scan line spacing, which is particularly advantageous for printer applications, for example.

Although the foregoing has been described with reference to an example where the frequencies f ₁ and f ₂ of the natural vibration mode have a "twice" relationship where the latter is approximately twice the former, the latter is "three times" approximately three times the former. Relationships can also be established. In this case, as in the "double" relationship, the sawtooth vibration becomes a vibration based on the superposition of sinusoids. Since this makes it possible to use reciprocal scanning of light, the number of scan lines at a certain available frequency can be doubled.

When driving as in the present embodiment is performed, the displacement angle must be stabilized while adjusting a plurality of natural vibration modes in a predetermined relationship. To this end, in this embodiment the light in the deflecting device, the second movable moment of inertia of the element (120), (I ₂₎ to the moment of inertia of the first movable element 102 about the oscillation axis 104 to the oscillation axis 104, It is made larger than (I ₁ ). By doing so, the two natural vibration modes can be easily adjusted to satisfy the desired relationship. This is the same as described above with reference to the embodiment of the present invention. Therefore, even when the two torsional natural vibration modes do not satisfy the desired relationship due to dispersion of fineness or the like caused in the manufacture of the optical deflector, by adjusting the moments of inertia I ₁ , I ₂ , for example, Torsional natural vibration mode can be adjusted to the desired frequency relationship.

In addition, by increasing the moment of inertia I ₂ , the amplitude amplification factor (resonance fineness Q value) of the natural vibration mode is improved. Accordingly, the stability of the displacement angle is improved by increasing the moment of inertia so as to increase the amplitude amplification rate to suppress the dispersion of vibration energy.

In the optical deflector of this embodiment, the length 122 of the second movable element 120 in the direction perpendicular to the vibration axis 104 is the length of the first movable element 102 in the direction perpendicular to the vibration axis 104. It can be made larger than (121). By doing so, the air resistance acting on the second movable element 120 is reduced and the displacement angle stability is further improved.

In addition, in the optical deflector of the present embodiment, the second movable element 120 is provided with a plurality of components (silicon part 103, hard magnetic material 108 and copper member 109), while the reflective surface 107 is provided. The formed first movable element 102 is provided by a single component. As a result, even if the second movable element 120 is deformed when the hard magnetic material 108 and the copper member 109 are attached to the silicon portion 103, this causes the reflective surface 107 of the first movable element 102 to be deformed. Do not deform. Therefore, the fall of the scanning light spot is prevented.

Second Embodiment

Next, an optical deflector according to a second embodiment of the present invention will be described with reference to FIGS. 4A and 4B. Fig. 4A is a plan view of the optical deflector of this embodiment and Fig. 4B is a sectional view taken along the line A-B in Fig. 4A. The optical deflector of the second embodiment has a structure substantially similar to that of the first embodiment, but the optical deflector of the present embodiment has two reflective elements 220a and 220b and a reflective surface around the oscillation axis 204. Torsion springs (205a, 205b, 206a, 206b) for elastically connecting the first movable element 202 and the second movable elements (220a, 220b) is formed. The second movable elements 220a and 220b have silicon portions 203a and 203b and film permanent magnets 208a and 208b, respectively.

The optical deflector of this embodiment is characterized in that the second movable elements 220a and 220b are thicker than the first movable element 202. In addition, the silicon portions 203a and 203b of the second movable elements 220a and 220b are thicker than the first movable element 202. The first movable elements 220a and 220b have a thickness of 100 μm and the second movable elements 203a and 203b have a thickness of 200 μm.

The support members 201a and 201b, the first movable element 202, the silicon portions 203a and 203b of the second movable elements 220a and 220b, and the torsion springs 205a, 205b, 206a and 206b are all single crystal silicon substrates. It is manufactured as a unitary structure. Therefore, an optical deflector with a very high processing precision and a compact size can be manufactured. These devices can be formed by photolithography and dry etching of a semiconductor manufacturing method. The film permanent magnets 208a and 208b include rare earth permanent magnets such as SmCo (cobalt samarium) and are formed by sputtering or the like.

In the optical deflector of this embodiment, the thickness of the silicon portions 203a and 203b of the second movable elements 220a and 220b is larger than that of the first movable element 202. This structure can make the moment of inertia of the second movable elements 220a and 220b larger than the first movable element 202 without attaching a metal member having a large moment of inertia to the second movable elements 220a and 220b. To ensure that. In this way, the torsional natural vibration frequency can be easily adjusted to satisfy the desired relationship.

4A and 4B, also in this embodiment, the lengths 222a and 222b of the second movable elements 220a and 220b in the direction perpendicular to the vibration shaft 204 are the vibration shaft 204. The length of the first movable element 202 is shorter than the length 221 of the first movable element 202. As a result, air resistance is reduced and displacement angle stability is improved. Since the movable element is supported at both ends in the structure of this embodiment, unnecessary vibration other than torsional vibration during torsional vibration is more reliably prevented.

Third Embodiment

Next, an optical deflector according to a third embodiment of the present invention will be described with reference to FIGS. 5A and 5B. Fig. 5A is a plan view of the optical deflector of this embodiment and Fig. 5B is a sectional view taken along the line A-B in Fig. 5A. The optical deflector of the third embodiment has a structure generally similar to that of the first embodiment, but the optical deflector of the present embodiment is formed by the second movable element 320 elastically connected to the support member 301 via the torsion spring 306. It differs from the first embodiment in that it has a portion 303 and hard magnetic bodies 308a and 308b. These hard magnetic bodies 308a and 308b are Fe-Cr-Co magnets in this embodiment.

The second movable element 320 of the optical deflector of the present embodiment is provided with a plurality of hard magnetic bodies, such as 308a and 308b, which are disposed via the vibration shaft 304 therebetween. Since the hard magnetic bodies 308a and 308b are made of Fe-Cr-Co having a large specific gravity, the moment of inertia of the second movable element 320 can be relatively easily increased.

In addition, in the present embodiment, since the hard magnetic bodies 308a and 308b are disposed at the positions as described above, it is easy to align the center of gravity of the second movable element 320 with the vibration shaft 304. Thus, unwanted vibrations other than torsional vibrations during torsional vibrations are more reliably prevented.

Since the hard magnetic material is used for the members 308a and 308b for increasing the moment of inertia of the second movable element 320, the necessary current to be applied to the coil to drive the optical deflector is lowered. Thus, an optical deflector operable with low power consumption is achieved.

In addition, the length 322 of the second movable element 320 in the direction perpendicular to the vibration axis 304 is the vibration of the first movable element 302 connected to the second movable element 320 via the torsion spring 305. It is shorter than the length 321 in the direction perpendicular to the axis (304). As a result, air resistance is reduced and displacement angle stability is improved.

In addition, the optical deflector may have a structure in which at least one of the first and second movable elements 302, 320 intersects the plane at a plurality of positions when a plane perpendicular to the vibration axis 304 is defined. Can be. For example, as shown by the thin dashed line in FIG. 5A, a plurality of protrusions are provided at the outer periphery of the movable element. Another example is a case in which a spindle shape extending in a direction parallel to the vibration shaft 304 is formed in the movable element as it moves away from the vibration shaft 304. In these structures, the moment of inertia around the oscillation shaft 304 can be easily increased. In order to adjust the mass of the movable element, the protrusion of the outer periphery can be removed, thereby enabling efficient mass control. The method can be used in other embodiments.

[Example 4]

Next, an optical deflector according to a fourth embodiment of the present invention will be described with reference to FIGS. 6A and 6B. Fig. 6A is a plan view of the optical deflector of this embodiment and Fig. 6B is a sectional view taken along the line A-B in Fig. 6A. The optical deflector of the fourth embodiment has a structure generally similar to that of the first embodiment, but the optical deflector of the present embodiment is connected to the support member 401 via the torsion spring 406 so that the second movable element 420 is silicon. It differs from the first embodiment in that it has a hard magnetic material 408a, 408b composed of a portion 403 and a Fe-Cr-Co magnet.

Therefore, also in this embodiment, the moment of inertia of the second movable element 420 elastically connected to the first movable element 402 via the torsion spring 406 can be easily increased. Also in this embodiment, since the plurality of hard magnetic bodies 408a and 408b are disposed via the vibration shaft 404, the center of gravity of the second movable element 420 can be easily aligned with the vibration shaft. Therefore, unnecessary vibration other than torsional vibration during torsional vibration is prevented. In addition, since the required current to be applied to the coil to drive the optical deflector is lowered, an optical deflector operable with low power consumption is achieved.

This embodiment differs from the first embodiment in the following two points. That is, the length 422 of the second movable element 420 in the direction perpendicular to the vibration axis 404 is shorter than the length 421 of the first movable element 402 in the direction perpendicular to the vibration axis 404. The length 422 of the second movable element 420 in the direction parallel to the vibration axis 404 is shorter than the length 423 of the first movable element 402 in the direction parallel to the vibration axis 404. As a result, air resistance is reduced and displacement angle stability is improved.

[Fifth Embodiment]

Fig. 7 is a schematic perspective view showing an embodiment of an optical apparatus incorporating an optical deflector according to the present invention. In this example, the image forming apparatus is shown as an optical mechanism. In Fig. 7, 503 indicates an optical deflector according to the present invention and the optical deflector functions to scan incident light in one dimension. 501 indicates a laser light source and 502 indicates a lens or lens group. 504 designates a recording lens or lens group and 505 designates a drum-type photosensitive member. 506 indicates a scan trajectory.

The laser beam emitted from the laser light source 501 is subjected to a predetermined intensity modulation related to the deflection scanning timing of the light. The intensity modulated light propagates through the lens or lens group 502 and is scan deflected one-dimensionally by an optical scanning system (light deflector) 503. The scan deflected laser beam is focused by a recording lens or lens group 504 on the photosensitive member 505 to form an image on the photosensitive member.

The photosensitive member 505 rotates in a direction perpendicular to the scanning direction about the rotation axis and is uniformly charged by a charging device not shown. By scanning the photosensitive member surface using light, an electrostatic latent image is formed on the scanned surface portion. Thereafter, by using the developing device, not shown, the toner image is generated in accordance with the electrostatic latent image, transferred to an unshown transfer paper, and fixed, so that the image is generated on the paper.

By using the optical deflector 503 of the present invention, the angular velocity of the deflection scan of the light can be made almost uniform in the effective area of the surface of the photosensitive member 505. In addition, by using the optical deflector 503 of the present invention, the image forming apparatus can perform a stable operation and generate a clear image.

Although the present invention has been described with reference to the structures disclosed herein, the present invention is not limited to the details and the present application encompasses changes or modifications for improvement purposes or within the scope of the following claims.

The optical deflector according to the present invention makes it possible to easily adjust a plurality of natural vibration modes in a desired relationship and provides an effect of stably maintaining the displacement angle even when the displacement angle is relatively large. In addition, the optical apparatus of the present invention using such an optical deflector has a large but stable displacement angle.

Claims (12)

Support member, A first movable element having an optical deflecting element, At least one second movable element, One or more first torsion springs configured to support the first and second movable elements for torsional vibration about an oscillation axis; At least one second torsion spring configured to support the second movable element and the support member for torsional vibration about the oscillation axis; A drive system configured to apply a drive force to one or both of the first and second movable elements, The moment of inertia of the second movable element with respect to the vibration axis is greater than the moment of inertia of the first movable element with respect to the vibration axis, The length of the second movable element in the direction perpendicular to the vibration axis is smaller than the length of the first movable element in the direction perpendicular to the vibration axis, The optical deflector has two or more natural vibration modes of different frequencies, And a permanent magnet provided only to a second movable element among the first movable element and the second movable element. The optical deflector of claim 1, wherein a length of the second movable element in a direction parallel to the vibration axis is less than a length of the first movable element in a direction parallel to the vibration axis. The optical deflector of claim 1, wherein the second movable element has a larger thickness than the first movable element. The optical deflector of claim 1, wherein the second movable element is constituted by a plurality of components. The optical deflector of claim 4, wherein the components of the second movable element are disposed between the oscillation axis. The optical deflector of claim 1, wherein the second movable element has a center of gravity aligned with an oscillation axis. The optical deflector of claim 1, wherein the first movable element, the second movable element, the first torsion spring, the second torsion spring, and the support member are made of monocrystalline silicon in an integrated structure. The optical deflector of claim 1, wherein the moment of inertia of the second movable element with respect to the vibration axis is four times greater than the moment of inertia of the first movable element with respect to the vibration axis. delete The optical deflector of claim 1, wherein the drive system is configured to torsionally vibrate the first movable element about a vibration axis simultaneously in the two or more natural vibration modes. The optical deflector according to claim 1, wherein one or both of the first movable element and the second movable element are provided with a plurality of protrusions at ends far from the vibration axis. With a light source, The optical deflector according to claim 1, One of the photosensitive member and the image display member; And the optical deflector is configured to deflect the light from the light source and direct some or all of the deflected light to the photosensitive member or the image display member.

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